Method of cooking corn dough tortillas using infrared radiation

ABSTRACT

Cooking of food products and particularly of dough-based food products such as corn tortillas is effected with a considerably reduced cooking time by applying to the uncooked food product infrared radiation waves simultaneously on both sides of the food product in order to quickly cook both surfaces of the same thus forming capping layers that retain a high degree of moisture within the body of the food product without unduly drying the same. The infrared radiation waves are preferably applied by means of an optical arrangement formed by two parallel arrays of infrared emitters, one on each side of the food product, said arrays of emitters having a plurality of resistive elements to generate said infrared radiation and optical reflectors to direct said radiation perpendicularly to both sides of the food product.

FIELD OF THE INVENTION

The present invention refers to the techniques for cooking food productsby the use of infrared radiation and, more particularly, it is relatedto a method and an apparatus for cooking dough-based products, such ascorn dough products (corn masa products) and particularly corntortillas, by the use of infrared (IR) radiation.

BACKGROUND OF THE INVENTION

Corn-based food and snack products are very well known in themarketplace and are generally made from several types of corn (maize)and mixtures of corn with other grains, These products include corntortillas, corn chips, taco shells, corn tostadas, corn puffs, and thelike, all of which are made from nixtamalized, rehydrated, andmicronized corn dough. The corn mixtures with other cereal grains mayinclude cornsorghum, corn-soybean, and corn-amaranth, as well as othergrain-enriched corn dough mixtures, including multi-grain mixtures. Theterm "corn dough" or "masa", as used in this application, means doughsmade from corn whether or not they contain other grains or additives.Similarly, the term "corn products", as used in the instant application,means those products made from corn with or without other grains oradditives.

Various methods for the preparation of a diversity of corn products arevery well known in the prior art and are well documented in theliterature, with some of them being proprietary techniques. The additionof flavorings, conditioners, as well as other additives andpreservatives, and the choice of shape are also very well known and willdepend on the characteristics desired for the product. These can serveto increase taste, nutritional values, shelf life and appearance.

As all of the above mentioned products, particularly the corn productssuch as corn tortillas need to be suitably cooked, various methods forcarrying out such cooking have been developed in the prior art. Theoldest one of said methods, which at least in Mexico may be dated backin the Tenth century, uses a so called "comal", which is a relativelyflat plate made from clay, metal or ceramic material, that was heated byburning wood, charcoal or other combustible materials available at thetime. In this very ancient method, the corn products, particularly corntortillas were shaped by hand to the desired form and placed on thecomal for a period of time sufficient to cook the same, turning themover at predetermined intervals with the aim of producing a uniformcooking on both sides. Obviously, the traditional methods such as theone described above, were generally batch processes.

In order to more clearly describe the type of cooking methods existentin the prior art, the cooking of corn tortillas will be taken as anexample of said cooking methods. Corn tortillas, which have been atraditional food product in several Latin American countries and thatare becoming more and more popular in other North American and Europeancountries, are round flat cooked pieces of corn dough, the dimensions ofwhich vary from one producer to the other, However, the preferreddimensions are 8 to 15 cm, in diameter, and 0.5 to 3 mm in thickness.The weight of corn tortillas is generally from 20 to 35 grams per piece.The moisture content of the uncooked corn dough used to make corntortillas, usually ranges from 40 to 52% by weight.

During comal cooking, the temperature range of the comal varies from180° to 210° C., depending on the type of comal used. When placing thetortilla for the first time in thermal contact with the comal, there isa formation of a thin vapor impervious or capping layer (a few tenths ofa millimeter thick) on the side of the tortilla in contact with thecomal. This layer seals the corresponding side against vapor exhaustion.Usually, the time to produce said layer will depend on the moisturecontent of the product and on the cooking temperature of the comal, andranges from 20 to 40 seconds. After this time has elapsed, the tortillais turned over to cook the other side. Cooking of the second side takesfrom 20 to 50 seconds. At this stage, another vapor impervious orcapping layer (from 0.5 to 1.9 millimeters thick) is produced. Theoverall cooking of the tortilla is considered as complete once theproduct inflates (puffs). The degree of puffing of the tortilla duringcooking, determines the efficiency of the cooking and the quality of thecooked tortilla. The capping layers are useful for retaining the correctmoisture within the product and hence the overall quality needed forshelf life and handling purposes. At the end of the cooking time,moisture levels of the tortilla are reduced by from 12 to 8% by weight.The productivity of this batch type method depends on the number oftortillas able to fit on the comal at any given time, and on the thermalconductivity of the dough being cooked.

Besides the comet method described above as admitted prior art,industrial methods for continuously cooking corn tortillas have beendescribed in several Mexican and U.S. patents. For instance, Mexicanpatent No. 15,798 issued during the year 1915 to Compania La India, S.A. and no longer available and therefore mentioned here as admittedprior art, for the first time introduces the continuous cooking oftortillas by providing a vertical cylindrical oven heated by wood or thelime, with a manually rotatable circular cover on which the tortillaswere placed, turned over and taken off by hand.

Mexican patent No. 19,628 issued during the year 1920 to C. Celorio etal, also not available and mentioned here as admitted prior art,introduces for the first time a rudimentary automatic machine for makingcorn tortillas, which uses conveyor belts running within a cookingtunnel heated by means of a plurality of gas burners.

During the year 1921 a machine using a plurality of rollers heated bymeans of internal gas oil burners was launched to the Mexican market,without much success in view of the fact that it was extremely difficultto form the capping layers between the several pairs of heating rollersthrough the nip of which the tortillas had to be passed.

Mexican patent No. 45,792 issued to Fausto Celorio during the year 1947,no longer available and mentioned here as admitted prior art, introducedfor the first time the use of a conveyor belt located within a cookingtunnel having a plurality of gas burners to heat the tortillas thatcontinuously run through said tunnel on said belt. Although Celorioaccomplishes a considerable improvement over the cooking methods andequipment prior to this invention, the machine still uses gas burnersdistributed along the path of the conveyor belt and the control of thetemperature was not very efficient, whereby the percentage of discardedproducts used to be relatively high.

Mexican patent 104,748 issued to Fausto Celorio on Oct. 9, 1970,describes an improved cooking device which includes a series of conveyorbelts having a series of burners for burning any type of fuel arrangedunder the stretches of the belts that transport the tortillas, and aseries of perforated articulated rollers which improve the distributionof hot gases to evenly cook the tortillas. Although this machineconstitutes a considerable improvement over the prior art, it stillmakes use of fuel burners, thus showing the same type of drawbacks shownby prior art devices, namely, difficult control of temperaturethroughout the device, long cooking times and occasional defectivecapping layers.

Mexican patent 123,272 issued to Fausto Celorio on Aug. 27, 1973,describes a cooking apparatus which includes air pre-heating means forpre-heating the air that is injected to the burners for providing oxygenfor the combustion of the fuel, but without changing the principle ofcooking the tortillas by means of the transportation thereof on conveyorbelts to be heated by the burners.

Mexican patent 125,047 issued to Fausto Celorio on Mar. 11, 1974,describes a tortilla making machine that includes a novel take-offdevice for the individual tortillas but without changing the principleof cooking the tortillas on conveyor belts by means of gas burners orburners for other fuels.

Mexican patent 135,461 issued to Fausto Celorio on Mar. 16, 1977describes an improved cooking chamber for cooking tortillas, saidchamber being formed by a group of conveyor belts carrying thetortillas, the burners for gas or other fuel being arranged along thebelts between the upper and lower stretches thereof, and the chamberbeing divided into a corresponding plurality of tunnels for formingisolated cooking sections for each conveyor belt, the partitionsdividing said chamber running from the inlet end to the outlet end ofsaid chamber and each partition being located such that each isolatedcooking section includes the lower stretch of the upper belt and theupper stretch of the next lower belt. Although the capacity ofproduction of this device is remarkably higher than that of the priorart cooking apparatus, it still preserves the same principle of cookingthe tortillas with burners for fuel.

Johnson, B. A., Rooney, L. W. and Khan, M. N., Journal of Food Science,Volume 45, 1980, make reference to the cooking of corn tortillas on page672, by stating that tortillas intended for immediate consumption andhaving capping layers are cooked on gas-heated griddles at a temperatureof 315° C., whereas "taco tortillas", that is, unpuffed tortillas, arecooked on said gas-heated griddles at a temperature of 247° C.,alternating sides at predetermined intervals. Again times of up to about2 minutes have to be used and the problem of repeatedly turning over thetortillas to accomplish a uniform cooking is not eliminated.

Tonella, M. L., Sanchez, M. and Salazar, M. G., Journal of Food Science,Volume 48, 1983, also make reference to the cooking of tortillas on page1638, but they go back to the traditional comal cooking method withoutsuggesting any improvement over said very ancient method.

Holt, S. D., Resurreccion, R. V. R. and McWatters, K. H., Journal ofFood Science, Volume 57, No. 1, 1992, describe on page 122 a method forcooking tortillas that comprises heating the tortillas on a non-stickelectrically heated griddle at 190° C. for 3 minutes on each side,turning over the tortillas every 90 seconds during the cooking periodand pressing each time with a metal spatula to remove air pockets. Thiscooking method, as reported by Holt et el, is intended for the obtentionof taco-type tortilla, that is unpuffed tortilla, and of course thecooking time and the need of pressing the tortilla are factors thatrender said method absolutely uneconomical.

Finally, U.S. Pat. No. 4,769,253 issued to Willard, M. J. on Sep. 6,1988 and U.S. Pat. No. 4,985,269 issued to Irvin, S. A., Fedor, R. A.and Merritt, C. G. on Jan. 15, 1991, both describe cooking methods fordough pieces to produce snacks or tortilla chips, which cooking methodsinclude the frying of the dough and not the mere heating thereof, thusconsiderably departing from the purpose of obtaining good quality corntortillas or the like.

None of the above mentioned references, therefore, suggests the cookingof the corn tortillas by the use of radio frequency energy, but ratheruse either electrical resistive heating or the traditional heating bycombustion of common fuels, either directly or through the previousheating of air which is then passed through the cooking zone.

Although some of the prior art methods described above are satisfactoryfor producing the capping layers on the tortilla, all of said methodsshow the important drawback that the conservation of moisture in thefinal product is deteriorated. The capping layers of the tortillasacquire the same rough surface of the hot conveyor belts due to thethermal diffusion mechanism utilized during the cooking operation.Another important drawback of these methods is the poor thermal energytransfer between the hot conveyor belt and the product, resulting in alimited productivity. The low thermal conductivity of the dough and theamount of the thermal energy wasted in heating up the conveyor beltsrender these processes slow and inefficient.

To overcome the drawbacks shown by the methods involving direct contactheating from a comal or from a hot conveyor belt as discussed above, andwith the aim of producing good sealed capping layers, others haveexplored the use of microwave radiation for heating the dough. Thismicrowave radiation methods unfortunately tend to dry the shaped doughwithout cooking the outside satisfactorily and produce a hard, tastelessand brittle undesirable tortilla having an unappealing appearance. Inview of these discouraging results, the use of high frequency radiationhas been disclosed by others not as a method of making tortillas butrather as a method for drying dough for purposes other than theproduction of soft edible dough products.

In view of the rather unsatisfactory results shown by the direct heatingmethods for the cooking of dough-based products such as corn tortillasand the unsuccessful intended use of high frequency radiation(microwaves) for said purpose, for long an effective cooking method hasbecome indispensable, which will overcome the above described drawbacksshown by the prior art methods of cooking this type of products,particularly corn tortillas, which method has not been found prior tothe advent of the present application,

OBJECTS OF THE INVENTION

Having in mind the defects of the prior art methods and apparatus forcooking corn dough based products, it is an object of the presentinvention to provide a method for cooking food products, particularlycorn dough based products, and still more particularly corn tortillas,which will considerably reduce the cooking time without howeverdecreasing the quality of the product.

Another object of the present invention is to provide a method forcooking food products, of the above described character, which willavoid the use of direct heating of the product by means of burners orthe like.

One other and more particular object of the present invention is toprovide a method of cooking food products, of the above mentionedcharacter, which will permit the use of infra red radiation for thecooking operation and yet will be sufficiently mild to produce soft andappealing cooked products.

One other and more particular object of the present invention is toprovide a method of cooking food products, of the above mentionedcharacter, which will very quickly cook the products without excessivedrying of the same.

Still another object of the present invention is to provide an apparatusfor cooking food products by means of infrared radiation, which will beof a very simple and economical construction and yet will provide a highefficiency and speed of cooking of the food products, without undulydrying same.

Other object of the present invention is to provide a method for theselection of an optimal frequency band, based on measurements of theoptical properties of the dough, which will provide a means for carryingout the method of cooking in the most efficient manner.

The foregoing objects and others ancillary thereto are preferablyaccomplished as follows:

According to a preferred embodiment of the present invention, a methodof cooking food products comprises:

a) Preparing a dough from meal or flour of the food product;

b) Cutting and shaping the dough into pieces of predetermined size andthickness;

c) Generating infrared radiation to be irradiated within a cooking spacefor the food product;

d) Selecting an optimal wavelength band of said infrared radiationdepending on the moisture content and the shape desired for the cookedfood product; and

e) Passing the uncooked food product through said cooking space at apredetermined speed in order to produce the desired degree of cooking ofthe same.

BRIEF DESCRIPTION OF THE DRAWINGS.

The novel features that are considered characteristic of the presentinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest be understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a block diagram showing the essential steps of the process inaccordance with the present invention for cooking food products; and

FIG. 2 is a diagrammatic cross sectional elevational view of anapparatus for carrying out the method of the present invention.

DETAILED DESCRIPTION

The method of the present invention that will be described in detailhereinafter, unexpectedly overcomes the drawbacks shown by all of themethods of the prior art discussed above. It has been discovered thatthere are wavelength band and infrared emitter configurations that allowthe energy to be beamed onto the dough in a predetermined pattern toaccelerate the cooking of the food product, and that if the cooking ofcorn tortillas is specifically considered, infrared emitters can also beconfigured to very quickly cook the outside surfaces thereof, thuseasily generating the customary vapor impervious capping Layers on bothsides of the tortilla early in the cooking process, in order to preventexcessive drying,

It is to be stressed that with the method of the present invention,satisfactory food products can be produced in approximately 10% of thetime required for the direct heating or microwave heating methods of theprior art. The method of the present invention is based on the use ofinfrared radiation energy for cooking food products, particularly cornproducts and still more specifically corn tortillas in a much shortertime but with the production of products having equal or superiorquality than those cooked by the conventional direct heating ormicrowave heating process.

The method of the present invention can be most efficiently carried outby selecting a particular infrared wavelength band which will depend onthe optical characteristics of the product, for application to the saidproducts by means of an infrared emitter which is suitably designed forcooking tortillas or other food products quickly and without excessivedrying. The selection of said particular wavelength band is based onmeasuring the optical properties of the dough that must be cooked forobtaining the desired food product, as will be described in more detailhereinafter.

Although the method of the present invention may be used for cooking anytype of food products, it is particularly efficient for cooking foodproducts derived from a dough and, still more particularly, for cookingfood products based on corn dough or masa, such as corn tortillas.Therefore, the following detailed description of certain embodiments ofthe method of cooking of the present invention will be mainly referredto corn dough products, although it must be understood that the methodof the present invention can be equally used for cooking other types offood products. For any of the corn dough products to be cooked, severalprevious steps must be carried out to optimize the speed and energyrequired in the cooking process.

The dough to be cooked must be prepared in such a way that it containsall additives, grains and other ingredients required. For thepreparation of a predetermined uncooked dough product, any methods knownto those skilled in the art can be used. Next, the dough products mustbe shaped in the desired geometry. For instance, when dealing with corntortillas, the traditional round and flat shape is generally obtained bymeans of any suitable presses, apparatus or methods also known to thoseskilled in the art.

As already mentioned above, the selection of an appropriate wavelengthband of the infrared radiation to be applied on the dough products forthe cooking of the same, heavily depends on the optical properties ofthe dough or masa. For corn dough based products, for instance, theoptical absorption factor possesses several maxima if a broad wavelengthrange is investigated. At wavelengths greater than 4 micrometers, thereis a sequence of maxima that change in amplitude with temperature, dueto evaporation of water molecules present in corn mixtures, Morespecifically, in the instance of uncooked corn tortillas prepared fromnixtamalized corn dough (masa) or dough made with dehydrated corn flour,it has been found that the formation of the capping layers before thetotal cooking of the tortillas is carried out, is effected under maximumemission within a preferred wavelength band of from about 1.5 to about 4micrometers. Within this wavelength band, the cooking of the tortillasis quite good regardless of the fact that the penetration is onlyseveral micrometers, mainly in view of the fact that the position of themaximum of the absorption factor within these wavelengths is essentiallyindependent of the temperature. For dough mixtures of differentcompositions, other maxima may exist above the above mentioned range ofwavelengths. The important feature to be considered for efficientlycooking food products by infrared radiation is to determine thewavelength band within which the absorption factor of the dough isrelatively independent from changes in the temperature, since otherwisethe IR wave absorption by said product will be low and therefore thecooking process would be rendered inefficient.

The power requirements of the infrared radiation source must be chosenaccording to the weight, the amount of moisture to be removed, thetemperature increase desired, and the time selected to cook the product.In order to determine the IR power requirements for the IR source, itmust be assumed that the uncooked tortilla is a preferably heterogeneousmixture of corn material and water. By finding out the moisture contentof the product, the effective absorption factor of said product may bedetermined by means of effective media theories known to those skilledin the art. In particular, for corn tortillas with 40% by weight ofmoisture content, the preferred values of the absorption factor are from40 to 60%. Since the cooking method for tortillas is a dehydrationprocess, enough IR energy must be delivered to the product to heat it upto the boiling point of water and also sufficient IR energy must besupplied to evaporate from 8 to 12% by weight of water therefrom. Thepreferred IR energy levels for cooking corn tortillas in accordance withthe present invention varies from 70 to 200 Joules per gram of productand the most preferred wavelength band with maximum emission is of from2 to 4 micrometers, with preferred residence times of from 20 to 30seconds per tortilla piece.

In order to satisfy the desired characteristics of handling andappearance of the final product, the total moisture content in theuncooked product must be controlled to the desired level. Usually theselevels vary from product to product. However, in accordance with thepresent invention, it has been found that a preferred moisture contentrange of from 40 to 52% by weight is quite suitable for an efficient IRcooking of the product.

The corn tortillas are exposed for cooking to the above describedwavelength band of IR radiation, by placing them on a continuousconveyor belt which passes between opposing IR radiators which will bedescribed in detail hereinbelow. Next, the power level of the IR energyis set in order to allow the formation of both capping layers on theproduct before total cooking of the tortilla is completed. Under theseconditions, the tortilla is cooked within a period of time of from 20 to40 seconds.

The configuration of the cooking apparatus must be such that the IRradiation will have a homogeneous distribution along the product andsuch that the said distribution be suitable to the thin and roundgeometry of the tortilla, so that the same may be evenly cooked.

During the cooking stage of corn tortilla products, a fast heating ofboth surfaces is essential for retaining a suitable moisture levelinside the tortilla. Thus, the IR radiation must be beamedperpendicularly to both surfaces of the uncooked dough, which isaccomplished by the use of a special IR emitter configuration. An arrayof lineal IR emitters having suitable dimensions to permit the IRradiation to be beamed perpendicularly to both sides of the tortilla,and with a radiation pattern controlled by means of IR opticalreflectors is considered to be the preferred embodiment of the presentinvention. Also, in view of the fact that the wavelength band which hasbeen found to be most efficient for cooking flat products such as corntortillas is of from about 1.5 to about 5 micrometers, the IR emittersmust be preferably set to a wavelength within said wavelength band, withpreferred IR energy levels of from 70 to 200 Joules per gram of product.The most important stage of the IR radiation cooking process is to allowthe IR fields to heat up only and cook the outermost thin layers of thedough, in order to create moisture retaining capping layers on bothfaces of the product and thus avoid dehydration of the innermost layersof the tortilla before they reach the water evaporation temperatureduring the final stages of the cooking cycle.

As already described above, the preferred frequency band of VLF radiowaves for cooking corn tortillas lies between 10 and 100 Khz and itappears that the reason why the cooking operation works efficientlywithin this frequency band is related to the fact that the dielectricdissipation factor for corn dough or masa is large within this range anddoes not change substantially in amplitude and frequency withtemperature up to about 110° C. Thus, in order to use the method of thepresent invention for cooking other food products, the dielectricproperties of such other products must be determined and particularlythe dissipation factor, which is the tangent of the ratio of therefraction index to the relative permitivity, within a suitable range offrequencies and temperatures. Methods to obtain the dissipation factorare standard methods known to those skilled in the art of dielectricmaterials. The dielectric losses must be preferably determined within afrequency range of from a few Hertz to several Megahertz, typically from10 Hz to 300 MHz. This measurement is repeated at various temperaturesfrom room temperature up to the value in which the food product is knownto be cooked. In particular, and according with this invention, for corntortillas the maximum temperature considered is around 100° C. Plottingthe dissipation factor of the food products versus frequency for eachtemperature, several maximum values of the dissipation factor will beobserved. For a fast cooking of the selected food product, it isnecessary to select a frequency at which the dissipation is a maximum.The selected maximum must be independent or practically independent oftemperature in the temperature range selected.

For cooking specific food products, the determination of the antennaconfiguration, either for batch or continuous production, is a functionof the specific geometry of the product. Therefore, the antennaconfiguration of the present invention is suitable only for thoseproducts having the specific geometry described above, that is, theabove described linear dipole array may be regarded as the mostefficient array for those food products in which the geometry is that ofa flat product, such as tortillas. Also, it has been found that saidantenna configuration is highly efficient for cooking other foodproducts having a relatively flat shape, such as wheat flour tortillas,as well as slices of meat, bread or cheese, sliced or choppedvegetables, potato chips, and the like. However, for cooking productswith irregular and invariable shapes other than planar, a differentantenna configuration which matches the product geometry must bedesigned in accordance with the above.

Having now more particular reference to the accompanying drawings, anembodiment of the method and the apparatus of the present invention willbe described as exemplified by the cooking of corn dough tortillas,although it must be understood that this is only illustrative but notlimitative of the scope of the present invention. FIG. 1 shows a blockdiagram illustrating the flow chart of a method for cooking corn doughtortillas. As diagrammatically shown in said figure, the method inaccordance with the present invention essentially comprises a doughpreparation step 1, a dough feeding step 2, a wavelength band selectionstep 3, and an infrared energy cooking step 4.

The dough is prepared as indicated in step 1 by the mixing andhomogenizing of the corn flour and the appropriate additives with thedesired amount of water to provide a suitable moisture content, and thencutting and shaping the dough into pieces of the desired shape. Themoisture content is one of the critical features of the method of thepresent invention, as already mentioned above. Knowledge of said factordetermines, in a later step, how a correct focusing of the IR radiationand the IR power level must be set to produce capping layers during thetortilla cooking step. With the correct amount of additives, moisturecontent, and shape, the dough is fed to a suitable belt conveyoraccording to step 2, The properties of the material with which theconveyor is built must be such that it will be able to maintain lowoxidation rates, low shadowing of the IR radiation, and such that itwill be able to withstand the cooking temperatures of the product. Instep 3 an appropriate wavelength band is selected for generating asuitable IR energy to be applied to a cooking zone through which theproduct is to be passed. The selected wavelength band, as alreadymentioned above, will depend on the nature of the food product to becooked. In the case of the preferred embodiment of the presentinvention, namely, the method for cooking corn tortillas, the wavelengthband is selected for cooking the product such that the two desiredcapping layers are created. Finally, in step 4 the dough pieces arepassed through a cooking zone where a suitable Level of IR energy isapplied by means of the IR emitters to said pieces for a time sufficientto cook the same.

FIG. 2 shows a preferred embodiment of an apparatus for IR cooking offood products. The apparatus built in accordance with this embodiment ofthe invention is highly suitable for cooking corn tortillas or otherflat food products and essentially comprises a conveyor belt 90 threadedaround and driven by a plurality of rollers 11 by means of a variablespeed drive, an IR optical configuration generally designated by thereference numeral 12 which comprises a specially arranged IR emitterconfiguration, an IR wavelength emission controller 13 and an AC powersource 14.

The previously prepared and shaped pieces 22 of corn dough if corntortillas are to be cooked or of other types of doughs if other flatfood products are to be cooked, are fed to the conveyor belt 10. Theconveyor belt 10 carries the uncooked pieces of dough 27 through acooking zone enclosed in a suitable thermally insulating casing 15 inwhich a plurality of specially arranged IR emitters such as 16 and 17 isinstalled as will be described in more detail hereinbelow. At this stagean infrared radiation energy is applied to the product, by means of theIR emitters 16 and 17 of the IR optical configuration 12.

One of the critical features of the apparatus in accordance with thepresent invention is the configuration of the IR emitters 16 and 17 forforming the optical IR configuration identified by the general referencenumeral 12, since as mentioned above, said configuration will depend onthe nature and characteristics of the product to be cooked. For cookingtortillas or food products having similar flat shapes, said optical IRconfiguration 92 preferably comprises two linear arrays of IR emitters,parallelly arranged to each other, one of said arrays being locatedabove the conveyor belt 10 and the other one below the conveyor belt 10as illustrated by the emitters 16 and 17, respectively, shown in FIG. 2.namely, one array 19, 21 located under the conveyor belt 10 and anotherarray 20, 22 located above the conveyor belt 10. The infrared waveenergy is generated by resistive elements such as 18 and 19 arrangedwithin the IR emitters 16 and 17, respectively, each such resistiveelement being connected in parallel to the AC power source 16 throughthe wavelength emission controller 13 by means of suitable lines 20 and21. The distance between the arrays of emitters can be varied accordingto the dimensions of the product to be cooked, and the length of saidemitters can be varied depending on the amount of material and the timeto cook the same, inasmuch as the black body intensity emission willdepend on the number of IR emitters present in the opticalconfiguration.

The emitters 16 and 17 are supported by a thermally insulated frame (notshown) and are provided with optical reflectors such as 26 and 27 andthe whole optical configuration 12 of IR emitters is enclosed in theabove mentioned thermally insulated housing 15, in order to minimizeheat losses to the exterior of the heating or cooking zone bounded byhousing 15.

The previously shaped uncooked dough pieces 22 are fed to the conveyorbelt 10 on one end thereof to be passed through the IR heating orcooking zone 15 between the two arrays of IR emitters 16 and 17 whichquickly heat the two faces of the flat dough piece beginning theswelling thereof as shown at 23, to thereafter form the upper cappinglayer as shown at 24 and finally forming the lower capping layer asshown at 25, when the product is cooked perfectly and constitutes afinished cooked product that is delivered by the belt 10 at the oppositeside of the apparatus, as shown in FIG. 2.

The present invention may be more clearly understood in the followingexample, which is given without any intention to restrict the invention,since said example must be regarded as merely illustrative but nonlimitative of the scope of this invention.

EXAMPLE

Freshly made, hydrated corn dough was prepared by mixing commercialinstant corn flour with water in a 1:1.25 ratio. The moisture contentwas determined by weighing a portion of the dough before and afterdehydration at 50° C. For 2 hours. The total moisture content for themixture was 42% by weight. The dough was converted into tortillas, thatis, into round and flat pieces of dough. For cooking the tortillas theywere deposited on a continuous conveyor belt made of stainless steelmesh made of 18 gauge wire, providing 18 squares per inch to minimizeshadowing of the IR radiation and the products were passed through thecooking zone of the cooking apparatus described in the specification andillustrated in FIG. 2 hereof. A wavelength band between 2.5 and 3.5micrometers was used for irradiating the IR energy to cook the dough.

The IR energy was irradiated on the dough by means of two linear arraysof 4 resistively heated IR emitters facing each other, each emitterhaving a length of 60 cm and a diameter of 3/8", and a distance ofseparation of 1". The emitters for each array were round and made from aNi-Cr alloy covered by a stainless steel sleeve and isolated with MgOceramic. The emitters were supported by a frame made of stainless steelmaterial and were provided with optical reflectors of polished stainlesssteel. The electrical power delivered to each one of said emitters wasof 900 VA, with which the corresponding surface temperature of eachresistive element was of about 1000° K., thus producing a black bodywavelength peak emission of 2.9 micrometers. This emission wascontrolled by a wavelength emission controller and the IR radiated powertransferred from each resistive element was of 5.5 watts/cm². A total IRpower of 20 watts/cm² was applied to the food product.

Under the above described conditions the cooking time for the corntortillas was of 20 seconds, after which time a completely puffed softand flexible tortilla was produced.

Although certain specific embodiments of the present invention have beenshown and described above, it is to be understood that manymodifications thereof are possible. The present invention, therefore, isnot to be restricted except insofar as is necessitated by the prior artand by the spirit of the appended claims.

What is claimed is:
 1. A method for cooking corn dough tortillas usinginfrared radiation comprising the steps of:a) preparing a corn dough tobe cooked, with a moisture content in the range of 40 to 52% by weight;b) cutting and shaping the dough with said moisture content in order toobtain pieces of uncooked corn tortillas of predetermined size andthickness; c) generating infrared radiation waves within a wavelengthrange of from 1.5 to 4 micrometers to be irradiated within a cookingspace for the uncooked corn tortilla; and d) passing the pieces ofuncooked corn tortillas through said cooking space at a predeterminedspeed in order to produce the desired degree of cooking of said piecesof uncooked corn tortillas.
 2. A method of cooking accordance to claim1, wherein said wavelength of said infrared radiation waves isrelatively independent to changes in temperature.
 3. A method of cookingaccording to claim 1 wherein said infrared radiation waves are generatedat an energy level of from about 70 to about 200 joules per gram of thecorn tortilla to be cooked.
 4. A method for cooking corn tortillascomprising the steps of:a) preparing a nixtamalized corn dough of a typesuitable for the manufacture of corn tortillas and having a moisturecontent of from about 40 to about 52% by weight; b) cutting and shapingthe corn dough in order to form flat and round dough pieces; c)generating infrared radiation waves within a wavelength band of fromabout 2.5 to about 3.5 micrometers. d) irradiating said infraredradiation waves with said wavelength band in a cooking space; and e)passing said dough pieces through said cooking space at a speed suchthat the residence time of the dough pieces in said cooking space is offrom about 20 to about 30 seconds.
 5. A cooking method according toclaim 4 wherein said infrared radiation waves are generated at an energylevel of from about 70 to about 200 Joules per gram of the corn doughpieces to be cooked.